How to use the R8 Keep Rule Analyzer agent skill

What is an agent skill and what does r8-analyzer do?

An agent skill is a folder of instructions and helper files that an AI coding agent loads when a task matches the skill's description. The r8-analyzer skill covers one job: finding keep rules that keep more code than necessary in an Android app.

R8 is the code shrinker in Android builds. Keep rules tell it what not to remove or rename. When the skill runs, it runs Google's R8 tooling to measure how many classes, fields and methods each rule protects, then writes a Markdown report flagging redundant rules, overly broad package-wide rules, and rules already covered by library consumer rules. It only recommends changes; a person has to verify and apply them.

• Flags redundant keep rules
• Flags broad package-wide rules
• Flags rules that subsume library consumer keep rules
• Reports impact metrics such as classes, fields and methods protected per rule

Install the r8-analyzer skill

Download the ZIP for the skill from this page and unzip it. Place the resulting folder in your personal skills directory, ~/.claude/skills/, or in a project's .claude/skills/ directory if you want the skill to apply only to that project.

If you use the Claude apps, you can instead upload the skill under Settings → Capabilities → Skills.

• Personal install: unzip into ~/.claude/skills/
• Project install: unzip into your project's .claude/skills/
• Claude apps: Settings → Capabilities → Skills, then upload

Check the requirements before you run it

The skill needs Python 3 and the protobuf Python package, version 6.33.4 or later. Install it with the command below. Your project must be an Android Gradle Plugin project that includes the Gradle wrapper (./gradlew).

If your AGP version is below 9.3, the skill's build-based path temporarily changes the R8 classpath in settings.gradle or settings.gradle.kts. That change must be reverted afterward. The skill is designed to ask for your confirmation before editing those files when it runs interactively.

• Python 3
• protobuf Python package 6.33.4 or later
• Android Gradle Plugin project with the Gradle wrapper
• For AGP below 9.3: a temporary R8 classpath change in settings.gradle(.kts) that must be reverted

Ask for the analysis in plain language

You do not need to type a command. Describe what you want from the agent while it has access to your project. The skill is meant to trigger when you want to reduce app size, remove redundant or overly broad keep rules, or troubleshoot ProGuard configurations.

Phrase requests around your goal. Examples include asking the agent to review your R8 keep rules for redundancies, to find keep rules that are too broad for your app size, or to work out why R8 keeps more code than you expect.

The skill does not handle general Gradle build errors, Compose UI performance, or runtime CPU profiling. Ask about those and it will not be the right tool.

• "Review the keep rules in this Android project and tell me which ones are redundant."
• "My release APK is too big. Check whether our R8 keep rules are too broad."
• "Why is R8 keeping so much code in our release build?"

Run the analysis and read the report

The skill chooses a path based on your AGP version. With AGP 9.3.0 or later, it runs a standalone Gradle task, converts the output to JSON, then analyzes it. With AGP below 9.3.0, it temporarily updates R8 in your settings file, generates the report, analyzes it and reverts the change.

The report is a Markdown document. It lists the rules it found, their impact metrics and guidance from the skill's rule reference. Review every suggested change and test your release build carefully before applying it.

• Analysis output is written under the project's tmp/ folder
• The report is shown in the chat and is not saved to a file by the skill
• Verify each recommendation with a release build and testing before changing rules

Safety notes: scripts and network

The skill runs Python scripts from its scripts/ directory, including analyze.py and convert_pb_to_json.py. It also runs Gradle commands in your project. According to its metadata, it does not use the network. Review the scripts yourself if your organisation requires it.

The skill is designed to create files only under tmp/ and to leave your project files unchanged, apart from the temporary settings change described above. If you do not want build files edited, tell the agent before it runs; the skill then reports rule-level findings without scores.

• Runs scripts: yes
• Uses network: no
• Writes to tmp/ only, apart from the temporary R8 settings change for AGP below 9.3